The present invention relates to the general subject matter of pressure relief devices and, more particularly, to rupture disks and rupture panels.
A rupture disk is a pressure relief device that is designed to fail by bursting at a predetermined pressure and temperature. In broad terms, a rupture disk may be thought of as a xe2x80x9cfusexe2x80x9d that is adapted for use with fluids under pressure, where xe2x80x9cfluidxe2x80x9d should be broadly interpreted to include gases and granular materials (such as grains, wood chips, etc.). In a typical application, the rupture disk is installed as part of a pressure vessel or network of pipes which contain fluid. When the pressure within the system exceeds certain predefined limits, the attached rupture disk fails and xe2x80x9cburstsxe2x80x9d open, thereby providing a passageway through which pressurized fluid can flow out of the system. Of course, bursting of the rupture diskxe2x80x94and the resulting removal of fluid from the systemxe2x80x94will have the general effect of reducing the internal pressure within the pipes and devices in the system, thereby reducing the risk of a catastrophic failure. General information related to the general field of rupture disks can be found in U.S. Pat. Nos. 5,002,088, 5,558,114, 5,720,380, and 5,411,158, the disclosures of which are incorporated herein by reference.
Each rupture disks is designed to burst at a particular fluid pressure. However, some manufacturing variability is expected and the range of pressures within which a given disk is expected to burst is given by the manufacturer as its xe2x80x9crupture tolerance.xe2x80x9d The tolerance is often expressed as a percentage of the nominal burst pressure of the disk and might be as low as a few percent or as high as 40 percent or more.
Rupture disks are generally made of a metals such as aluminum or steel, although many variations are available. The operating portion of the disk is usually generally shaped like a hemisphere or dome and is formed of very thin material, with the thickness of the material determining in a general way the pressure at which the disk will burst. (Obviously, other things being equal, the thicker the metal in the dome the more resistant the disk would be to pressure-induced bursting). Rupture disks that have burst must be discarded and cannot be reused.
Rupture disks are available in a wide of variety of configurations, but one of the more popular arrangements involves the use of a rupture disk and holder combination. Depending on the particular rupture disk, when the rupture disk is installed into a system it may be clamped between two thick flanges which are referred to collectively as the rupture disk holder. In a typical configuration, the holder is sized to be bolted within standard ANSI pipe flanges and fit within the bolt circle. Holders are made of a durable material such as carbon steel and they are not discarded when the rupture disk fails, but rather are retained for use with the replacement disk. Holders may be reused indefinitely, but for safety reasons the disks installed therein are normally replaced at least once a year.
Rupture panels are so-called because they usually take the shape of rectangular panels, rather than round disks. Conventionally, rupture panels are offered in two different configurations: flat panels and crowned panels, the later of which is bowed outward. In actuality, they perform the same general function as rupture disks, although at possibility different pressure ranges and in different sized openings. Thus, in the text that follows the terms rupture disk and rupture panel will be used interchangeably to refer to pressure-relieving devices for use on a pressure vessel, pipeline network, etc.
The functional portion of a conventional rupture panel is constructed of three layers: two (usually identical) metal layers (typically made of thin sheets of steel) are separated by a seal made of a thin material such as Dupont""s Teflon (TM) fluoropolymer resin product (e.g., Teflon of about 0.005 inches thick would be typical). In the argot of the trade, the panel most distant from the contained fluid is conventionally known as the xe2x80x9ctop sectionxe2x80x9d, the seal is known as the xe2x80x9clinerxe2x80x9d, and the panel nearest the pressurized fluid is known as the xe2x80x9cback pressure supportxe2x80x9d (or xe2x80x9cvacuum supportxe2x80x9d). The vacuum support member is so-called because it is designed to support the liner when the pressure in the vessel goes below the pressure outside of the vessel and the normally outward directed forces are reversed.
In a typical configuration, a pattern of slits is systematically cut into both of the rupture panel metal layers to weaken them to the point where they will fail together at approximately a predetermine fluid pressure. Although this arrangement does allow a panel or disk to be manufactured that fails at a designated over pressure, it has the general disadvantage introducing holes into the panel that can leak fluid therethrough.
Of course, and as is well know to those of ordinary skill in the art, the function of the liner is to contain the fluid so that the slits do not leak. Additionally, the cuts in the panels are covered by xe2x80x9cslit coversxe2x80x9d or xe2x80x9cslot coversxe2x80x9d, flat strips of metal (e.g., aluminum) that are adhered or welded over the cuts in the panel. This might be done for many reasons, but one of the primary reasons is that this prevents fluid pressure from pushing the thin film seal out through the slits in the panel opposite the pressurized fluid, thereby damaging the seal.
One disadvantage of the conventional two-panel configuration is that it is relatively expensive to build, as it requires the manufacture of two precision-cut panels which must thereafter be carefully assembled.
Additionally, it is conventional to use a separate gasket along with the rupture panel to seal it around its outer perimeter. As is well known to those skilled in the art, it is important to seal the rupture disk where it attaches to the pressurized system to prevent leakage therefrom. In a conventional arrangement, the rupture panel will be equipped with a metal flange or frame to which the gasket is matched. The gasket might be made from a wide range of synthetic materials, including plastics and elastomers. Of course, if the gasket is installed improperly or is defective, leaks can occur and may occasion the need to remove the entire unit and reinstall it at some expense. Additionally, the separate gasket does add some cost to the rupture disk assembly.
Finally, the thin sealing material tends to creep through the slits in the metal top section in response to pressure against it. When this happens, the liner may abrade and leak at pressures below those for which the panel was designed. Additionally, the pressure of the liner on the outer metal section may cause a bulging in that member which can result in an undesired stress on the slots or slits cut therein. This stress may cause that section to deform or to rupture at unpredicted pressures.
Heretofore, as is well known in the pressure relief industry, there has been a need for an invention to address and solve the above-described problems. Accordingly, it should now be recognized, as was recognized by the present inventor, that there exists, and has existed for some time, a very real need for a device that would address and solve the above-described problems.
Before proceeding to a description of the present invention, however, it should be noted and remembered that the description of the invention which follows, together with the accompanying drawings, should not be construed as limiting the invention to the examples (or preferred embodiments) shown and described. This is so because those skilled in the art to which the invention pertains will be able to devise other forms of this invention within the ambit of the appended claims.
There is provided hereinafter an improved rupture panel or disk that consists of a sheet metal top section with a relatively thick polymer foam sealing liner attached thereto. That is, in the preferred arrangement the instant invention does not require a separate support member. The foam sealing component is preferably attached to the top section by some sort of adhesive to hold it in place and it is installed on the process side of the top section. Additionally, the sealing member is preferably of a thickness which is substantially thicker than would typically be used in a conventional rupture disk arrangement. The preferred thickness and material of this member helps keep it from being pushed through the slits in the top section, which would be a problem with conventional thin-sealing member. Finally, in another preferred embodiment the sealing member is also designed to function as a gasket, thereby eliminating the need for that separate member.
According to another preferred embodiment, there is provided a rupture panel or disk substantially as described above, but wherein a second sealing componentxe2x80x94which is preferably also made of polymer foamxe2x80x94is adhered to the other side of the panel top section, thereby creating a xe2x80x9csandwichxe2x80x9d of metal surrounded by two, preferably identical, foam sealing members.
The foregoing has outlined in broad terms the more important features of the invention disclosed herein so that the detailed description that follows may be more clearly understood, and so that the contribution of the instant inventor to the art may be better appreciated. The instant invention is not to be limited in its application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. Rather, the invention is capable of other embodiments and of being practiced and carried out in various other ways not specifically enumerated herein. Additionally, the disclosure that follows is intended to apply to all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. Further, it should be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting, unless the specification specifically so limits the invention. Further objects, features, and advantages of the present invention will be apparent upon examining the accompanying drawings and upon reading the following description of the preferred embodiments.